[TowerTalk] Balun Recommendation

[Jim Thomson]

Date: Fri, 13 Apr 2012 17:06:11 +0100
From: Steve Hunt <steve at karinya.net>
Subject: Re: [TowerTalk] Balun Recommendation

Some designs here:
http://www.karinya.net/g3txq/chokes/

8 turns on a FT240-31 core is good for 20m thru 10m - it gives >2k Ohm 
choking impedance across the range and is predominantly resistive.

Steve G3TXQ



On 12/04/2012 17:10, Tom Harke wrote:
> I am in the process of building a number of OWA's for 10,15 and 20 meters.
> I am looking for a recommendation for a good current balun.
>
> Thanks

## Steve, does this mean 8 turns of RG- 58 on a single core.  Will a single core even handle
1.5 kw CCS  CXR + SWR.    RG-58 is junk, so it would have to be wound with RG-303 teflon coax
or similar. 

##  what about using .25 or .75  or  1.25 wavelength of coax, with the shield bonded to the top of the tower. 
I mean a physical .25 or .75   or 1.25 wavelength...   minus 2%.   The Z at the feed point would be sky high.
Then no requirement for a conventional balun  at all. 

##  His OWA yagis  are all monobanders, so cutting a .25-.75-1.25 wave length of  coax for each band
is no big deal.  It just has to reach from the feed point to the top of the tower.   That will depend on
how long the booms are.  Use a good bulk head type connector at the top of the tower, and the bulk head
connector can then also be used to interface to the  heliax or what ever cable he uses to run down the
side of the tower. 

##  4 turns of  RG-393 or RG-213 on 4 stacked FT-240-31 cores will also work, provide they are well
away from the boom.  If they are mounted dead center in a  nema box, then no stray C to boom. 

##  22 x  type 43  beads, of the  1.125 inch long x 1 inch diam  x .515 inch ID   variety, slid over RG-213
or  RG-393 coax will also work.   Slid over RG-393, and you will never overheat them.., not even with 10 kw.  

Jim   VE7RF